In conventional labeling machines, a continuous strip of label material is gripped and pulled at its leading edge by a rotating label transport drum, and an individual label is severed therefrom by cutting means located ahead of the drum. Transverse ridges or projections on the label transport drum press the label against a glue applicator and then press the leading edge of the label against a container. The label is then released and wrapped around the container.
In many labeling operations, the label is wrapped completely around the container so that the trailing edge overlaps the leading edge. Often in such cases, it is desirable to use one type of adhesive at the leading edge to adhere the label to the material of the container and another type of adhesive at the trailing edge that would be better adapted to adhere the two overlapping portions of the label together. For example, where certain plastic labels are applied to containers it has been found advantageous to seal the overlapped edges by applying a solvent to finite areas of the trailing edge to form a tacking solution. As described in Fumel U.S. Pat. No. 4,567,681, this bond becomes stronger as the solution solidifies and facilitates subsequent heat shrinking of the label. The Fumel patent also discusses the advantages of just a temporary bond between the leading edge of the label and the container itself so that the label can be easily removed for recycling the container, and it teaches the use of the same solvent for the leading edge as well.
However, since a hot melt glue will stick the leading edge of the label to the container instantly while such solvent takes time to set, there are distinct advantages in using separate sealing media for high speed production. With present vacuum drums, wherein the radial projections are fixed, only one glue wheel can be used.